The present invention relates to an ion generating apparatus.
Ion generating apparatuses have previously been used for cleaning, disinfection and deodorization of the air in rooms or automobiles. Most of such apparatuses have an AC power source portion, a step-up transformer and a needle electrode, all of which being housed in an enclosure, in which a high AC voltage raised by the transformer is applied to the needle electrode to thereby activate corona discharge, and ions generated by the discharge are emitted from an ion emitting hole opened in the enclosure. Both negative ions and positive ions are possibly generated by the ion generating apparatus, where negative ions are generally believed to be more excellent in cleaning, deodorizing and disinfectant effects.
A problem will however arise in that airborne dust, oil or other dirty matters may adhere onto the ion generating electrode so as to finally cover the discharge plane thereof during a long-term use of such ion generating apparatus. Once such situation occurs, the discharge for generating ions will badly be interfered, which may result in lowered ion generation efficiency, and more worse discontinuance of the ion generation.
Japanese Laid-Open Patent Publication No. 11-111427 discloses an apparatus having a needle cathode for generating ions and a grounded anode opposed thereto to thereby generate negative ions, in which the distance between both ends of the cathode and anode positioned in parallel is properly adjusted to thereby successfully prevent dirt adhesion, as well as to suppress ozone smell and to raise the negative ion generation efficiency. In this prior art, a problem however resides in that the dirt adhesion onto the needle cathode per se cannot be prevented at all.
It is therefore an object of the present invention to provide an ion generating apparatus capable of removing dirt adhered on the ion generating electrode in a simple and effective manner, and furthermore capable of efficiently preventing the ion generation efficiency from being degraded due to dirt adhesion or suppressing of such degradation.
To solve the foregoing problems, an ion generating apparatus of the present invention is characterized in that comprising an ion generating electrode for generating negative ions while being applied with a negative high voltage; a high-voltage generating portion for ion generation for applying high voltage for generating ions to the ion generating electrode; and an electric cleaning mechanism for burning out attachment adhered on the ion generating electrode by electric heating.
According to the constitution of the present invention, the electric cleaning mechanism is provided to burn out dirt adhered on the ion generating electrode through electric heating, so that the dirt can be removed in a thorough and simple manner, and thus the apparatus can successfully prevent the ion generation efficiency from being degraded due to dirt adhesion. In particular, in case of the ion generating electrode having a sharp end, dirt adhesion to such portion where the ion generating field concentrates will considerably ruin the ion generating efficiency. Burning out of the attachment on the end portion of the ion generating electrode using the electric cleaning mechanism will be extremely beneficial to avoid such nonconformity. In this case, an object of the cleaning will be attained to a sufficient degree if only the dirt adhered onto the sharp end portion of the electrode, which is responsible for the ion generation, is selectively removed, which is also advantageous in simplifying the apparatus since there is no need to excessively raise the electric heating capacity of the electric cleaning mechanism.
The ion generating electrode may also be composed so as to generate ions by corona discharge using an counter electrode. The counter electrode in this case may also function as a dust collecting electrode. On the other hand, such composition may not always ensure a desirable ion generating efficiency since generated negative ions may be attracted by the counter electrode and may adhere thereon or decompose. So that, it is advantageous to compose the ion generating electrode as a lone electrode without being accompanied by any counter electrode for discharge, in terms of raising the ion generating efficiency if the dust collecting electrode is not specifically needed. While a mode of electric discharge for generating ions in this case may be understood as analogous to corona discharge, it is different in a precise meaning from generally-understood corona discharge since no apparent counter electrode is involved. However in many cases, a discharge mode similar to corona discharge may be established since some conductive members outside the apparatus can eventually act as the counter electrode even though such members were not intended for functions of an electrode.
The electric cleaning mechanism may be such that comprising a spark-discharge counter electrode for spark discharge located as being opposed to the ion generating electrode, and a spark-discharge, high-voltage generating portion for applying high voltage for the spark discharge between the ion generating electrode and the spark-discharge counter electrode, so that the attachment adhered on the ion generating electrode can be burnt out by spark-by-discharge generated between such ion generating electrode and such spark-discharge counter electrode upon being applied with a high voltage. Using spark discharge, heat generated by spark can efficiently be concentrated on the surface of the electrode to thereby remove the adhered dirt in a more complete manner. The ion generating electrode having a sharp end is advantageous in activating spark discharge for the cleaning without failure if such sharp end, where the electric field tends to concentrate, is opposed with the spark-discharge counter electrode.
An opposition distance (referred to as xe2x80x9cgap distancexe2x80x9d, hereinafter) between the ion generating electrode and the spark-discharge counter electrode during spark discharge depends on the magnitude of applied voltage, where a preferable range thereof for ensuring desirable spark generation is 2 mm or less, and more preferably 1 mm or less for applied voltage of up to 4,000 V or around. Spark for the discharge may be generated in a continuous manner, or intermittent manner so as to avoid excessive temperature rise of the electrode.
It is allowable for such case to provide a moving mechanism for the spark-discharge counter electrode which relatively moves it closer to or more distant from the ion generating electrode at least between a furthest position allowing ion generation from the ion generate electrode and a closest position allowing generation of the spark-by-discharge between the spark-discharge counter electrode and ion generating electrode. Keeping the spark-discharge counter electrode away from the ion generating electrode during the ion generation will successfully prevent undesirable spark discharge from occurring during a period essentially responsible for the ion generation. It is, however, also allowable to fix the gap distance between the spark-discharge counter electrode and the ion generating electrode, and to activate spark discharge by applying a higher voltage than that for the ion generation.
The electric cleaning mechanism may be such that including a resistance heating mechanism for burning out attachment adhered on the ion generating electrode by heating such ion generating electrode through resistance heating. By effecting resistance heating in at least an area to be cleaned of the ion generating electrode, the attachment such as dirt can efficiently be removed. The resistance heating mechanism may be such that comprising a current-fed member movable between a contact position allowing it to contact with the ion generating electrode and a distant position apart from such ion generating electrode, and a power source portion for current-fed heating for feeding electric current via such current-fed member to the ion generating electrode for resistance heating while being contacted with such ion generating electrode. In particular, in the case of the ion generating electrode having a sharp end, temperature of such end portion of the electrode, which is critical for the ion generation, can selectively be elevated by feeding current via the current-fed member contacted to such end portion having a gradually reducing sectional area, which eventually ensures the attachment removal (cleaning) for the end portion of the electrode at a small electric power without failure.
The ion generating apparatus of the present invention may have an automatic cleaning mechanism control portion capable of automatically activating, according to a predetermined timing, the electric cleaning mechanism so as to clean the ion generating electrode. This allows automatic cleaning of the ion generating electrode, and facilitates keeping of such electrode always in a clean condition.
In the ion generating apparatus of the present invention, the high-voltage generating portion may be composed of a transformer. While the transformer may be of wire-wound type, it is also preferable to use a piezoelectric transformer having on a piezoelectric ceramic device board an input terminal and an output terminal, whereby primary AC input voltage applied to the input terminal is raised by being mediated by mechanical vibration of such piezoelectric ceramic device board to the secondary AC output voltage to be output through the output terminal towards the ion generating electrode. The piezoelectric transformer, having no core and coiled portion, is compact and lightweight, which is advantageous in downsizing and weight reduction of the ion generating apparatus. In the case the ion generating apparatus is used as being incorporated into an air conditioner for cooling and heating as described later, such piezoelectric transformer can readily be assembled using a free space within the air conditioner since a circuit board of the ion generating mechanism can markedly be downsized.
Ozone generation due to silent discharge in the air will considerably increase in particular when the applied voltage has a high frequency with alternating polarity. In the case a wire-wound transformer is used, leakage magnetic field which alternatively changes depending on AC frequency tends to reach a higher level since the secondary side of the transformer has a larger number of turn in order to generate high voltage. If the ion generating electrode is placed within such leakage magnetic field, the ozone generation may be enhanced due to high-frequency current induced within the ion generating electrode. Using the piezoelectric transformer having no wound wire by nature may be successful in reducing a leakage magnetic field level sensible by the ion generating electrode, and thus may be more advantageous in suppressing the ozone generation.
The ion generating apparatus of the present invention may have a polarity conversion means for converting the secondary AC output voltage so as to ensure negative predominance of the polarity of voltage applied to the ion generating electrode. The polarity conversion means may be composed of a rectifying means which rectifies secondary AC output from the piezoelectric transformer so as to typically allow charge transfer having a directionality of negatively charging up the ion generating electrode but inhibit charge transfer having an opposite directionality. Further providing a condensing means for condensing negative charge, derived from the secondary AC output of the piezoelectric transformer, to be applied to the ion generating electrode will ensure stable generation of negative ions since the ion generating electrode can constantly be supplied with a negative voltage above a certain level. Combining such condensing means with the foregoing rectifying means will ensure more advanced level of stability in negative high voltage to be applied to the ion generating electrode, which can considerably downsize the apparatus as typically compared with the case of using a specialized high-voltage DC power source.